Test coverage measures the amount of testing performed by a set of test. Wherever we can count things and can tell whether or not each of those things has been tested by some test, then we can measure coverage and is known as test coverage. [Read more…]
Structure based techniques serve two purposes: test coverage measurement and structural test case design.
- They are often used first to assess the amount of testing performed by tests derived from specification-based techniques, i.e. to assess coverage.
- They are then used to design additional tests with the aim of increasing the test coverage.
- Structure-based test design techniques are a good way of generating additional test cases that are different from existing tests.
- They can help ensure more breadth of testing, in the sense that test cases that achieve 100% coverage in any measure will be exercising all parts of the software from the point of view of the items being covered.
As its name implies, exploratory testing is about exploring, finding out about the software, what it does, what it doesn’t do, what works and what doesn’t work. The tester is constantly making decisions about what to test next and where to spend the (limited) time.
This is an approach that is most useful when there are no or poor specifications and when time is severely limited.
- Exploratory testing is a hands-on approach in which testers are involved in minimum planning and maximum test execution.
- The planning involves the creation of a test charter, a short declaration of the scope of a short (1 to 2 hour) time-boxed test effort, the objectives and possible approaches to be used.
- The test design and test execution activities are performed in parallel typically without formally documenting the test conditions, test cases or test scripts. This does not mean that other, more formal testing techniques will not be used. For example, the tester may decide to us boundary value analysis but will think through and test the most important boundary values without necessarily writing them down. Some notes will be written during the exploratory-testing session, so that a report can be produced afterwards.
- Test logging is undertaken as test execution is performed, documenting the key aspects of what is tested, any defects found and any thoughts about possible further testing.
- It can also serve to complement other, more formal testing, helping to establish greater confidence in the software. In this way, exploratory testing can be used as a check on the formal test process by helping to ensure that the most serious defects have been found.
- Exploratory testing is described in [Kaner, 2002] and [Copeland, 2003] Other ways of testing in an exploratory way (‘attacks’) are described in [Whittaker, 2002].
The Error guessing is a technique where the experienced and good testers are encouraged to think of situations in which the software may not be able to cope. Some people seem to be naturally good at testing and others are good testers because they have a lot of experience either as a tester or working with a particular system and so are able to find out its weaknesses.
This is why an error guessing approach, used after more formal techniques have been applied to some extent, can be very effective. It also saves a lot of time because of the assumptions and guessing made by the experienced testers to find out the defects which otherwise won’t be able to find.
- The success of error guessing is very much dependent on the skill of the tester, as good testers know where the defects are most likely to be.
- This is why an error guessing approach, used after more formal techniques have been applied to some extent, can be very effective. In using more formal techniques, the tester is likely to gain a better understanding of the system, what it does and how it works. With this better understanding, he or she is likely to be better at guessing ways in which the system may not work properly.
- Typical conditions to try include division by zero, blank (or no) input, empty files and the wrong kind of data (e.g. alphabetic characters where numeric are required). If anyone ever says of a system or the environment in which it is to operate ‘That could never happen’, it might be a good idea to test that condition, as such assumptions about what will and will not happen in the live environment are often the cause of failures.
- A structured approach to the error-guessing technique is to list possible defects or failures and to design tests that attempt to produce them. These defect and failure lists can be built based on the tester’s own experience or that of other people, available defect and failure data, and from common knowledge about why software fails.
In experience based techniques, people’s knowledge, skills and background are of prime importance to the test conditions and test cases. [Read more…]
Structure-based testing technique is also known as ‘white box testing’ or ‘glass-box’ testing technique because here the testers require knowledge of how the software is implemented, how it works. [Read more…]
Use case testing is a technique that helps us identify test cases that exercise the whole system on a transaction by transaction basis from start to finish. They are described by Ivar Jacobson in his book Object-Oriented Software Engineering: A Use Case Driven Approach [Jacobson, 1992]. [Read more…]
State transition testing is used where some aspect of the system can be described in what is called a ‘finite state machine’. This simply means that the system can be in a (finite) number of different states, and the transitions from one state to another are determined by the rules of the ‘machine’. This is the model on which the system and the tests are based. [Read more…]
The techniques of equivalence partitioning and boundary value analysis are often applied to specific situations or inputs. However, if different combinations of inputs result in different actions being taken, this can be more difficult to show using equivalence partitioning and boundary value analysis, which tend to be more focused on the user interface. The other two specification-based software testing techniques, decision tables and state transition testing are more focused on business logic or business rules. [Read more…]
Technically, because every boundary is in some partition, if you did only boundary value analysis you would also have tested every equivalence partition. However, this approach may cause problems if that value fails – was it only the boundary value that failed or did the whole partition fail?
Also by testing only boundaries we would probably not give the users much confidence as we are using extreme values rather than normal values. The boundaries may be more difficult (and therefore more costly) to set up as well. [Read more…]